ИСТИНА

Identification of sources responsible for the observed particulate pollution levels is crucial for protection of public health in megacities because high population density and socioeconomic activities result in numerous emission sources. In northern megacity peculiar climatological characteristics related to heating system operation, much fuel consumption and population activity make it an important issue for the assessment by advanced aerosol characterization.The aim of this study is to identify the pollution sources of PM10 in the European largest northernmost megacity and quantify their contribution to the observed aerosol concentration levels. It should be noted that this is the first source apportionment study performed for the Moscow where centralizing gas-fuelled heating system operates during cold seasons, biomass and coal does not used in residential sector, despite of other European megacities. 24hr PM10 samples were collected during spring of 2018, autumn and winter of 2019-2020 at the Aerosol Complex of Moscow State University, classified as urban background site. Samples were analysed for (i) major and trace elements by ICP-MS, ICP-AES and XRF, (ii) OC and EC by thermo-optical transmittance method, and (iii) major ionic species by IC. PM10 concentrations were measured by TEOM 1400a. Various approaches, such as chemical mass balance, polar plots, positive matrix factorization (PMF), trajectory clustering were employed for characterizing aerosol speciation, identifying meteorological influence and sources origin, and apportioning contributions from each source. PM10 concentrations were higher during spring (29 ± 16 μg/m3) associated to soil resuspention after the snow cover melted , followed by autumn (20 ± 9 μg/m3) and winter (14 ± 6 μg/m3). Distinctive various aerosol speciation are associated to seasonality. Soil dust waxes in spring and wanes in summer, K+ acts as a marker of fires in spring as well as of the domestic biomass burning in the region around a megacity in autumn and winter. Secondary aerosol components always dominate over all the other inorganic ion species. Salt components (Na+ and Cl-) are attributed to de-icing agents used in road management. The best PMF solution corresponds to six sources: Traffic, Road salting, City/road dust, Industrial, Biomass burning, and Secondary. Polar plots show the variation of the source origin jointly with wind speed and wind direction (Fig.1). Traffic is identified by low OC/EC and tracers Zn, Ba and Sb, with maximum observed at weak wind conditions typical for non-buoyant ground-level source. Road salting relates to Na+ and Cl- with its source located on the highway in the northwest. City/road dust contains crustal elements Al, Ca, Ti, Fe together with anthropogenic Cu, Zn, Pb and has maximum in the direction of the city centre. Industrial profile contains EC, OC, Ni, Cu and Cr with biggest impact from the est. Biomass burning is identified by the presence of K+ and high OC/EC, its source in the south well correlates with trajectory clustering in SW in spring and SE in autumn and winter. Secondary aerosol formation source contains mainly SO42-, NO3-, NH4+, OC and is indicated in the southeast where the most industrially developed area takes place in Moscow